1. Field of the Invention
The invention relates to selectively steerable and maneuverable crawler apparatus and methods for visually inspecting pipe interiors and capturing images thereof with cameras under control of a human-machine interface (HMI). More particularly the invention is directed to crawler apparatus and methods for visually inspecting steam turbine engine cross over pipe interiors, including weld fillets on the under and top sides of flow guides formed between transverse and descending sections in the pipe.
2. Description of the Prior Art
FIGS. 1 and 2 show a known steam turbine 20, including a cross over pipe 22 having an inlet port 23 within a transverse section 24 of the pipe that transition to a bend section 25 and a descending section 26. A flow guide 28 is interposed between the transverse 24 and descending 26 sections of the pipe 22 and is affixed to the pipe inner circumferential wall by weld fillets 29. During periodic engine 20 services, it is desired to inspect periodically pipe 22 interior circumferential wall, upper and lower surfaces of the flow guide 28 and its weld fillets 29 as well as turbine blades 30. Wheeled crawler vehicles employing cameras have been inserted in pipes to perform visual inspections of their interior circumferences. Traditional wheel vehicles have difficulties gaining sufficient traction to be maneuvered with the pipe interior. To overcome traction difficulties in pipe interiors U.S. Pat. No. 5,551,349 describes a pipe crawler vehicle that utilizes a pair of forward and rear Mechanum-type wheels (described in U.S. Pat. No. 3,876,255) having rotational axes parallel to the vehicle longitudinal axis. The vehicle maneuvers in a straight line by screw-like wheel motion, but does not appear to be selectively steerable within a pipe. A vehicle without steering capability would not be able to circumnavigate a pipe surface in order to crawl on the upper surface of a steam cross over pipe flow guide 28. Inspection bore scopes have also been inserted into turbine engine cross over pipes 22, but they are cumbersome to maneuver through the pipe transition to either the upper or the lower surfaces of the flow guide 28, or to descend down the descending section 26.